Well, after seeing this D. W. Griffith film, it seemed very odd to me that the same director who apparently despised Black people had a very sensitive place in his heart for the German-speaking people following WWI. By the way, if you don't believe me about the "despised Black people" comment, try watching his films BIRTH OF A NATION and HIS TRUST. In both films, the Black actors are in fact Whites wearing makeup. In BIRTH OF A NATION, Blacks are shown as being evil and lazy and out to rape the White women if left unchecked by the wonderful KKK. In HIS TRUST, a Black slave acts like a lapdog in his devotion to his White "betters".
So, despite this awful baggage, it was shocking to see how favorably the former enemy were treated in this film. The main characters are Germans who had lived in land previously part of the old Germany--now part of Poland. They moved back to their ethnic homeland and settled into an impoverished Berlin. This sensitivity towards America's former enemy actually mirrored the change in attitude in general in the US, as people were now reassessing their role in the war and many felt, in hindsight, that we should have just stayed neutral.
The film shows the daily privations of this family as they just try to survive. Starvation and the difficulties of existing, interestingly enough, do NOT destroy or diminish their humanity--though it does do this to some of their fellow countrymen. This abiding faith and goodness in the face of adversity is why the film is entitled "ISN'T LIFE WONDERFUL". And, despite Griffith's tendency to often use "schmaltz" and heavy-handed melodrama in his films, this is a pretty restrained and beautiful movie.